Insulated flexible conductor and method of producing same



Oct. 2, 1928. 1,686,098

' F. MEIWALD INSULATED FLEXIBLE CONDUCTOR AND METHOD OF PRODUCING SAME Filed April 29, 1927 Zwenfw Fan; M'ec w b u y Fifvmey at... ca. 2, was. I 'UNlTED STATES I 1,686,098 PATENT OFFICE.

FRAIN 'Z MEIWALD, O1 VIENNA, AUSTRIA.

INSULATED FLEXIBLE CONDUCTOR AND- METHOD OI" PRODUCING SAME.

Application med Apri1 29, 1927, Serial No.

Heretofore the conductors of telephone wires or the like have been provided with understood it is illustrated in the accom panying drawing,'which shows the manner in which the new flexible conductor is built up.

It is already known to insulate certain kinds of cables and conductors by means of guttapercha,'but this mode of insulation as heretofore employed is not suited for conductors of particular flexibility because gutta-percha becomes porous and brittle during the use in the event of a non-airtight closure. Also the common practice of manufacturing cables by enclosin a solid copper conductor b a number of ayers of different kinds of abrics or'materials cannot be satisfactorily used in the case of very flexible conductors, such as telephone wires or the like. As it is well known the cable is stiffened by luting together the threads of the winding, consisting of any fibrous material, by subsequently coating or varnishing the same with resin, gutta-percha or similar sticky materials. This stiffness is objectionable in the case of a conducting line which, in contra-distinction to the cable, is designed to remain especially flexible and the conductor of which consists for instance of fine wires for securing extreme flexibility. According to the present invention the imroved flexible conductor, which comprises in the well known association the central core or carrier thread 1, thestranded wires 2, the inner cotton covering 3, the close cot ton sheath or serving 5, and the outer braided covering 6, is additionally generally strengthened and im roved in its insulating capacity, without impairment of its flexibility, by the provision of a covering 4. of thin gutta-percha tape which is wound in relatively steepalfi pitched helical edge-over:

lapping turns along the conductor upon 189,731, andYin Austria December 14, 1928.

the inner cotton covering 3, as clearly shown in the drawing. The overlapping edge portions of the turns are not ermanently united, which insures perfect iexibility at all times and avoidance of injury or interruption in the continuous sheathing thus provided between the coverings 3 and 5.

Telephone wires insulated in this manner with very pliant gutta-percha tape as thin as paper are just as flexible as the wires produced according to the known method, but compared with the latter they show the insulation-values indicated in the following table, whereby A designates the samples according to the known method and B designates the samples manufactured according to the present invention.

Insula- Insulation resist-tion resist- Number Twisted ance in ance in Sample of 0011- length in megohm megohm ductors metres at 70% at 100% air-moisair-moisture ture In the Government Testing Institute at Vienna the cables or conductors have been tested for 24; hours at a temperature of the room of 16 degrees centigrade, whereby the moisture of the air has been as indicated in theabove table.

The conductor produced according to the present invention shows to 400 times the insulation-resistance, compared with the known conductors, whereby not only a quite novel technical effect is obtained, but also an economical effect in consequence of its longer life.

On using the conductors accordmg to the present invention a large part of 2. A low-current flexible conductor comprising a flexible metallic conductor core, a covering, and an insulator between the covering and the core and consisting of an edge lapped tissue-thin helically wound guttapercha strip directly enveloping the core.

3. A method of making a flexible conductor so as to insulate the conducting element without impairing the flexibility of said element, which comprises interposing between a suitable outer fabric covering and the conducting element and disposing in contact with the latter a substantially tissuethin helically-wound edge-lapped insulating band of gutta-percha.

4.. A flexible conductor comprising a conductor core, a suitable outer fabric covering, and an insulating band of substantially tissue-thin gutta-percha between the conductor core and cover and helically wound 20 about the conductor core with the edges of its windings overlapping.

In testimony whereof I afiix my signature.

FRANZ MEIWALD. 

